Abstract
Morphine administration increased markedly the locomotor activity of mice. Pretreatment of mice with reserpine (5 mg/kg i.p., 24 hours) or with α-methyl-p-tyrosine (200 mg/kg i.p., three hours) decreased markedly the activity-increasing effects of morphine. Pretreatment with pargyline (100 mg/kg i.p., three hours) caused a slight shift to the left in the dose-response curve of morphine. In contrast, pretreatment of mice with either reserpine or pargyline caused no significant change in the activity-increasing effects of d-amphetamine. Pretreatment with α-methyl-p-tyrosine caused a shift to the right in the dose-response curve of d-amphetamine but did not decrease the maximum response obtained. The study suggests that certain effects of morphine are mediated by the release of catecholamines from adrenergic neurons in the brain. The present evidence also suggests that the activity-increasing effects of morphine are mediated by mechanisms different from those which mediate the effects of d-amphetamine.
Footnotes
- Received March 11, 1971.
- Accepted June 19, 1973.
- © 1973 by The Williams & Wilkins Company
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